/*
 * Copyright (C) 2010 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.actionbarsherlock.internal.nineoldandroids.animation;

import android.os.Handler;
import android.os.Looper;
import android.os.Message;
import android.util.AndroidRuntimeException;
import android.view.animation.AccelerateDecelerateInterpolator;
import android.view.animation.AnimationUtils;
import android.view.animation.Interpolator;
import android.view.animation.LinearInterpolator;

import java.util.ArrayList;
import java.util.HashMap;

/**
 * This class provides a simple timing engine for running animations which
 * calculate animated values and set them on target objects.
 * <p>
 * There is a single timing pulse that all animations use. It runs in a custom
 * handler to ensure that property changes happen on the UI thread.
 * </p>
 * <p>
 * By default, ValueAnimator uses non-linear time interpolation, via the
 * {@link AccelerateDecelerateInterpolator} class, which accelerates into and
 * decelerates out of an animation. This behavior can be changed by calling
 * {@link ValueAnimator#setInterpolator(TimeInterpolator)}.
 * </p>
 */
@SuppressWarnings({
        "rawtypes", "unchecked"
})
public class ValueAnimator extends Animator {

    /**
     * Internal constants
     */

    /*
     * The default amount of time in ms between animation frames
     */
    private static final long DEFAULT_FRAME_DELAY = 10;

    /**
     * Messages sent to timing handler: START is sent when an animation first
     * begins, FRAME is sent by the handler to itself to process the next
     * animation frame
     */
    static final int ANIMATION_START = 0;

    static final int ANIMATION_FRAME = 1;

    /**
     * Values used with internal variable mPlayingState to indicate the current
     * state of an animation.
     */
    static final int STOPPED = 0; // Not yet playing

    static final int RUNNING = 1; // Playing normally

    static final int SEEKED = 2; // Seeked to some time value

    /**
     * Internal variables NOTE: This object implements the clone() method,
     * making a deep copy of any referenced objects. As other non-trivial fields
     * are added to this class, make sure to add logic to clone() to make deep
     * copies of them.
     */

    // The first time that the animation's animateFrame() method is called. This
    // time is used to
    // determine elapsed time (and therefore the elapsed fraction) in subsequent
    // calls
    // to animateFrame()
    long mStartTime;

    /**
     * Set when setCurrentPlayTime() is called. If negative, animation is not
     * currently seeked to a value.
     */
    long mSeekTime = -1;

    // TODO: We access the following ThreadLocal variables often, some of them
    // on every update.
    // If ThreadLocal access is significantly expensive, we may want to put all
    // of these
    // fields into a structure sot hat we just access ThreadLocal once to get
    // the reference
    // to that structure, then access the structure directly for each field.

    // The static sAnimationHandler processes the internal timing loop on which
    // all animations
    // are based
    private static ThreadLocal<AnimationHandler> sAnimationHandler = new ThreadLocal<AnimationHandler>();

    // The per-thread list of all active animations
    private static final ThreadLocal<ArrayList<ValueAnimator>> sAnimations = new ThreadLocal<ArrayList<ValueAnimator>>() {
        @Override
        protected ArrayList<ValueAnimator> initialValue() {
            return new ArrayList<ValueAnimator>();
        }
    };

    // The per-thread set of animations to be started on the next animation
    // frame
    private static final ThreadLocal<ArrayList<ValueAnimator>> sPendingAnimations = new ThreadLocal<ArrayList<ValueAnimator>>() {
        @Override
        protected ArrayList<ValueAnimator> initialValue() {
            return new ArrayList<ValueAnimator>();
        }
    };

    /**
     * Internal per-thread collections used to avoid set collisions as
     * animations start and end while being processed.
     */
    private static final ThreadLocal<ArrayList<ValueAnimator>> sDelayedAnims = new ThreadLocal<ArrayList<ValueAnimator>>() {
        @Override
        protected ArrayList<ValueAnimator> initialValue() {
            return new ArrayList<ValueAnimator>();
        }
    };

    private static final ThreadLocal<ArrayList<ValueAnimator>> sEndingAnims = new ThreadLocal<ArrayList<ValueAnimator>>() {
        @Override
        protected ArrayList<ValueAnimator> initialValue() {
            return new ArrayList<ValueAnimator>();
        }
    };

    private static final ThreadLocal<ArrayList<ValueAnimator>> sReadyAnims = new ThreadLocal<ArrayList<ValueAnimator>>() {
        @Override
        protected ArrayList<ValueAnimator> initialValue() {
            return new ArrayList<ValueAnimator>();
        }
    };

    // The time interpolator to be used if none is set on the animation
    private static final/* Time */Interpolator sDefaultInterpolator = new AccelerateDecelerateInterpolator();

    // type evaluators for the primitive types handled by this implementation
    // private static final TypeEvaluator sIntEvaluator = new IntEvaluator();
    // private static final TypeEvaluator sFloatEvaluator = new
    // FloatEvaluator();

    /**
     * Used to indicate whether the animation is currently playing in reverse.
     * This causes the elapsed fraction to be inverted to calculate the
     * appropriate values.
     */
    private boolean mPlayingBackwards = false;

    /**
     * This variable tracks the current iteration that is playing. When
     * mCurrentIteration exceeds the repeatCount (if repeatCount!=INFINITE), the
     * animation ends
     */
    private int mCurrentIteration = 0;

    /**
     * Tracks current elapsed/eased fraction, for querying in
     * getAnimatedFraction().
     */
    private float mCurrentFraction = 0f;

    /**
     * Tracks whether a startDelay'd animation has begun playing through the
     * startDelay.
     */
    private boolean mStartedDelay = false;

    /**
     * Tracks the time at which the animation began playing through its
     * startDelay. This is different from the mStartTime variable, which is used
     * to track when the animation became active (which is when the startDelay
     * expired and the animation was added to the active animations list).
     */
    private long mDelayStartTime;

    /**
     * Flag that represents the current state of the animation. Used to figure
     * out when to start an animation (if state == STOPPED). Also used to end an
     * animation that has been cancel()'d or end()'d since the last animation
     * frame. Possible values are STOPPED, RUNNING, SEEKED.
     */
    int mPlayingState = STOPPED;

    /**
     * Additional playing state to indicate whether an animator has been
     * start()'d. There is some lag between a call to start() and the first
     * animation frame. We should still note that the animation has been
     * started, even if it's first animation frame has not yet happened, and
     * reflect that state in isRunning(). Note that delayed animations are
     * different: they are not started until their first animation frame, which
     * occurs after their delay elapses.
     */
    private boolean mRunning = false;

    /**
     * Additional playing state to indicate whether an animator has been
     * start()'d, whether or not there is a nonzero startDelay.
     */
    private boolean mStarted = false;

    /**
     * Flag that denotes whether the animation is set up and ready to go. Used
     * to set up animation that has not yet been started.
     */
    boolean mInitialized = false;

    //
    // Backing variables
    //

    // How long the animation should last in ms
    private long mDuration = 300;

    // The amount of time in ms to delay starting the animation after start() is
    // called
    private long mStartDelay = 0;

    // The number of milliseconds between animation frames
    private static long sFrameDelay = DEFAULT_FRAME_DELAY;

    // The number of times the animation will repeat. The default is 0, which
    // means the animation
    // will play only once
    private int mRepeatCount = 0;

    /**
     * The type of repetition that will occur when repeatMode is nonzero.
     * RESTART means the animation will start from the beginning on every new
     * cycle. REVERSE means the animation will reverse directions on each
     * iteration.
     */
    private int mRepeatMode = RESTART;

    /**
     * The time interpolator to be used. The elapsed fraction of the animation
     * will be passed through this interpolator to calculate the interpolated
     * fraction, which is then used to calculate the animated values.
     */
    private/* Time */Interpolator mInterpolator = sDefaultInterpolator;

    /**
     * The set of listeners to be sent events through the life of an animation.
     */
    private ArrayList<AnimatorUpdateListener> mUpdateListeners = null;

    /**
     * The property/value sets being animated.
     */
    PropertyValuesHolder[] mValues;

    /**
     * A hashmap of the PropertyValuesHolder objects. This map is used to lookup
     * animated values by property name during calls to
     * getAnimatedValue(String).
     */
    HashMap<String, PropertyValuesHolder> mValuesMap;

    /**
     * Public constants
     */

    /**
     * When the animation reaches the end and <code>repeatCount</code> is
     * INFINITE or a positive value, the animation restarts from the beginning.
     */
    public static final int RESTART = 1;

    /**
     * When the animation reaches the end and <code>repeatCount</code> is
     * INFINITE or a positive value, the animation reverses direction on every
     * iteration.
     */
    public static final int REVERSE = 2;

    /**
     * This value used used with the {@link #setRepeatCount(int)} property to
     * repeat the animation indefinitely.
     */
    public static final int INFINITE = -1;

    /**
     * Creates a new ValueAnimator object. This default constructor is primarily
     * for use internally; the factory methods which take parameters are more
     * generally useful.
     */
    public ValueAnimator() {
    }

    /**
     * Constructs and returns a ValueAnimator that animates between int values.
     * A single value implies that that value is the one being animated to.
     * However, this is not typically useful in a ValueAnimator object because
     * there is no way for the object to determine the starting value for the
     * animation (unlike ObjectAnimator, which can derive that value from the
     * target object and property being animated). Therefore, there should
     * typically be two or more values.
     * 
     * @param values A set of values that the animation will animate between
     *            over time.
     * @return A ValueAnimator object that is set up to animate between the
     *         given values.
     */
    public static ValueAnimator ofInt(int... values) {
        ValueAnimator anim = new ValueAnimator();
        anim.setIntValues(values);
        return anim;
    }

    /**
     * Constructs and returns a ValueAnimator that animates between float
     * values. A single value implies that that value is the one being animated
     * to. However, this is not typically useful in a ValueAnimator object
     * because there is no way for the object to determine the starting value
     * for the animation (unlike ObjectAnimator, which can derive that value
     * from the target object and property being animated). Therefore, there
     * should typically be two or more values.
     * 
     * @param values A set of values that the animation will animate between
     *            over time.
     * @return A ValueAnimator object that is set up to animate between the
     *         given values.
     */
    public static ValueAnimator ofFloat(float... values) {
        ValueAnimator anim = new ValueAnimator();
        anim.setFloatValues(values);
        return anim;
    }

    /**
     * Constructs and returns a ValueAnimator that animates between the values
     * specified in the PropertyValuesHolder objects.
     * 
     * @param values A set of PropertyValuesHolder objects whose values will be
     *            animated between over time.
     * @return A ValueAnimator object that is set up to animate between the
     *         given values.
     */
    public static ValueAnimator ofPropertyValuesHolder(PropertyValuesHolder... values) {
        ValueAnimator anim = new ValueAnimator();
        anim.setValues(values);
        return anim;
    }

    /**
     * Constructs and returns a ValueAnimator that animates between Object
     * values. A single value implies that that value is the one being animated
     * to. However, this is not typically useful in a ValueAnimator object
     * because there is no way for the object to determine the starting value
     * for the animation (unlike ObjectAnimator, which can derive that value
     * from the target object and property being animated). Therefore, there
     * should typically be two or more values.
     * <p>
     * Since ValueAnimator does not know how to animate between arbitrary
     * Objects, this factory method also takes a TypeEvaluator object that the
     * ValueAnimator will use to perform that interpolation.
     * 
     * @param evaluator A TypeEvaluator that will be called on each animation
     *            frame to provide the ncessry interpolation between the Object
     *            values to derive the animated value.
     * @param values A set of values that the animation will animate between
     *            over time.
     * @return A ValueAnimator object that is set up to animate between the
     *         given values.
     */
    public static ValueAnimator ofObject(TypeEvaluator evaluator, Object... values) {
        ValueAnimator anim = new ValueAnimator();
        anim.setObjectValues(values);
        anim.setEvaluator(evaluator);
        return anim;
    }

    /**
     * Sets int values that will be animated between. A single value implies
     * that that value is the one being animated to. However, this is not
     * typically useful in a ValueAnimator object because there is no way for
     * the object to determine the starting value for the animation (unlike
     * ObjectAnimator, which can derive that value from the target object and
     * property being animated). Therefore, there should typically be two or
     * more values.
     * <p>
     * If there are already multiple sets of values defined for this
     * ValueAnimator via more than one PropertyValuesHolder object, this method
     * will set the values for the first of those objects.
     * </p>
     * 
     * @param values A set of values that the animation will animate between
     *            over time.
     */
    public void setIntValues(int... values) {
        if (values == null || values.length == 0) {
            return;
        }
        if (mValues == null || mValues.length == 0) {
            setValues(new PropertyValuesHolder[] {
                PropertyValuesHolder.ofInt("", values)
            });
        } else {
            PropertyValuesHolder valuesHolder = mValues[0];
            valuesHolder.setIntValues(values);
        }
        // New property/values/target should cause re-initialization prior to
        // starting
        mInitialized = false;
    }

    /**
     * Sets float values that will be animated between. A single value implies
     * that that value is the one being animated to. However, this is not
     * typically useful in a ValueAnimator object because there is no way for
     * the object to determine the starting value for the animation (unlike
     * ObjectAnimator, which can derive that value from the target object and
     * property being animated). Therefore, there should typically be two or
     * more values.
     * <p>
     * If there are already multiple sets of values defined for this
     * ValueAnimator via more than one PropertyValuesHolder object, this method
     * will set the values for the first of those objects.
     * </p>
     * 
     * @param values A set of values that the animation will animate between
     *            over time.
     */
    public void setFloatValues(float... values) {
        if (values == null || values.length == 0) {
            return;
        }
        if (mValues == null || mValues.length == 0) {
            setValues(new PropertyValuesHolder[] {
                PropertyValuesHolder.ofFloat("", values)
            });
        } else {
            PropertyValuesHolder valuesHolder = mValues[0];
            valuesHolder.setFloatValues(values);
        }
        // New property/values/target should cause re-initialization prior to
        // starting
        mInitialized = false;
    }

    /**
     * Sets the values to animate between for this animation. A single value
     * implies that that value is the one being animated to. However, this is
     * not typically useful in a ValueAnimator object because there is no way
     * for the object to determine the starting value for the animation (unlike
     * ObjectAnimator, which can derive that value from the target object and
     * property being animated). Therefore, there should typically be two or
     * more values.
     * <p>
     * If there are already multiple sets of values defined for this
     * ValueAnimator via more than one PropertyValuesHolder object, this method
     * will set the values for the first of those objects.
     * </p>
     * <p>
     * There should be a TypeEvaluator set on the ValueAnimator that knows how
     * to interpolate between these value objects. ValueAnimator only knows how
     * to interpolate between the primitive types specified in the other
     * setValues() methods.
     * </p>
     * 
     * @param values The set of values to animate between.
     */
    public void setObjectValues(Object... values) {
        if (values == null || values.length == 0) {
            return;
        }
        if (mValues == null || mValues.length == 0) {
            setValues(new PropertyValuesHolder[] {
                PropertyValuesHolder.ofObject("", (TypeEvaluator)null, values)
            });
        } else {
            PropertyValuesHolder valuesHolder = mValues[0];
            valuesHolder.setObjectValues(values);
        }
        // New property/values/target should cause re-initialization prior to
        // starting
        mInitialized = false;
    }

    /**
     * Sets the values, per property, being animated between. This function is
     * called internally by the constructors of ValueAnimator that take a list
     * of values. But an ValueAnimator can be constructed without values and
     * this method can be called to set the values manually instead.
     * 
     * @param values The set of values, per property, being animated between.
     */
    public void setValues(PropertyValuesHolder... values) {
        int numValues = values.length;
        mValues = values;
        mValuesMap = new HashMap<String, PropertyValuesHolder>(numValues);
        for (int i = 0; i < numValues; ++i) {
            PropertyValuesHolder valuesHolder = values[i];
            mValuesMap.put(valuesHolder.getPropertyName(), valuesHolder);
        }
        // New property/values/target should cause re-initialization prior to
        // starting
        mInitialized = false;
    }

    /**
     * Returns the values that this ValueAnimator animates between. These values
     * are stored in PropertyValuesHolder objects, even if the ValueAnimator was
     * created with a simple list of value objects instead.
     * 
     * @return PropertyValuesHolder[] An array of PropertyValuesHolder objects
     *         which hold the values, per property, that define the animation.
     */
    public PropertyValuesHolder[] getValues() {
        return mValues;
    }

    /**
     * This function is called immediately before processing the first animation
     * frame of an animation. If there is a nonzero <code>startDelay</code>, the
     * function is called after that delay ends. It takes care of the final
     * initialization steps for the animation.
     * <p>
     * Overrides of this method should call the superclass method to ensure that
     * internal mechanisms for the animation are set up correctly.
     * </p>
     */
    void initAnimation() {
        if (!mInitialized) {
            int numValues = mValues.length;
            for (int i = 0; i < numValues; ++i) {
                mValues[i].init();
            }
            mInitialized = true;
        }
    }

    /**
     * Sets the length of the animation. The default duration is 300
     * milliseconds.
     * 
     * @param duration The length of the animation, in milliseconds. This value
     *            cannot be negative.
     * @return ValueAnimator The object called with setDuration(). This return
     *         value makes it easier to compose statements together that
     *         construct and then set the duration, as in
     *         <code>ValueAnimator.ofInt(0, 10).setDuration(500).start()</code>.
     */
    public ValueAnimator setDuration(long duration) {
        if (duration < 0) {
            throw new IllegalArgumentException("Animators cannot have negative duration: "
                    + duration);
        }
        mDuration = duration;
        return this;
    }

    /**
     * Gets the length of the animation. The default duration is 300
     * milliseconds.
     * 
     * @return The length of the animation, in milliseconds.
     */
    public long getDuration() {
        return mDuration;
    }

    /**
     * Sets the position of the animation to the specified point in time. This
     * time should be between 0 and the total duration of the animation,
     * including any repetition. If the animation has not yet been started, then
     * it will not advance forward after it is set to this time; it will simply
     * set the time to this value and perform any appropriate actions based on
     * that time. If the animation is already running, then setCurrentPlayTime()
     * will set the current playing time to this value and continue playing from
     * that point.
     * 
     * @param playTime The time, in milliseconds, to which the animation is
     *            advanced or rewound.
     */
    public void setCurrentPlayTime(long playTime) {
        initAnimation();
        long currentTime = AnimationUtils.currentAnimationTimeMillis();
        if (mPlayingState != RUNNING) {
            mSeekTime = playTime;
            mPlayingState = SEEKED;
        }
        mStartTime = currentTime - playTime;
        animationFrame(currentTime);
    }

    /**
     * Gets the current position of the animation in time, which is equal to the
     * current time minus the time that the animation started. An animation that
     * is not yet started will return a value of zero.
     * 
     * @return The current position in time of the animation.
     */
    public long getCurrentPlayTime() {
        if (!mInitialized || mPlayingState == STOPPED) {
            return 0;
        }
        return AnimationUtils.currentAnimationTimeMillis() - mStartTime;
    }

    /**
     * This custom, static handler handles the timing pulse that is shared by
     * all active animations. This approach ensures that the setting of
     * animation values will happen on the UI thread and that all animations
     * will share the same times for calculating their values, which makes
     * synchronizing animations possible.
     */
    private static class AnimationHandler extends Handler {
        /**
         * There are only two messages that we care about: ANIMATION_START and
         * ANIMATION_FRAME. The START message is sent when an animation's
         * start() method is called. It cannot start synchronously when start()
         * is called because the call may be on the wrong thread, and it would
         * also not be synchronized with other animations because it would not
         * start on a common timing pulse. So each animation sends a START
         * message to the handler, which causes the handler to place the
         * animation on the active animations queue and start processing frames
         * for that animation. The FRAME message is the one that is sent over
         * and over while there are any active animations to process.
         */
        @Override
        public void handleMessage(Message msg) {
            boolean callAgain = true;
            ArrayList<ValueAnimator> animations = sAnimations.get();
            ArrayList<ValueAnimator> delayedAnims = sDelayedAnims.get();
            switch (msg.what) {
            // TODO: should we avoid sending frame message when starting if we
            // were already running?
                case ANIMATION_START:
                    ArrayList<ValueAnimator> pendingAnimations = sPendingAnimations.get();
                    if (animations.size() > 0 || delayedAnims.size() > 0) {
                        callAgain = false;
                    }
                    // pendingAnims holds any animations that have requested to
                    // be started
                    // We're going to clear sPendingAnimations, but starting
                    // animation may
                    // cause more to be added to the pending list (for example,
                    // if one animation
                    // starting triggers another starting). So we loop until
                    // sPendingAnimations
                    // is empty.
                    while (pendingAnimations.size() > 0) {
                        ArrayList<ValueAnimator> pendingCopy = (ArrayList<ValueAnimator>)pendingAnimations
                                .clone();
                        pendingAnimations.clear();
                        int count = pendingCopy.size();
                        for (int i = 0; i < count; ++i) {
                            ValueAnimator anim = pendingCopy.get(i);
                            // If the animation has a startDelay, place it on
                            // the delayed list
                            if (anim.mStartDelay == 0) {
                                anim.startAnimation();
                            } else {
                                delayedAnims.add(anim);
                            }
                        }
                    }
                    // fall through to process first frame of new animations
                case ANIMATION_FRAME:
                    // currentTime holds the common time for all animations
                    // processed
                    // during this frame
                    long currentTime = AnimationUtils.currentAnimationTimeMillis();
                    ArrayList<ValueAnimator> readyAnims = sReadyAnims.get();
                    ArrayList<ValueAnimator> endingAnims = sEndingAnims.get();

                    // First, process animations currently sitting on the
                    // delayed queue, adding
                    // them to the active animations if they are ready
                    int numDelayedAnims = delayedAnims.size();
                    for (int i = 0; i < numDelayedAnims; ++i) {
                        ValueAnimator anim = delayedAnims.get(i);
                        if (anim.delayedAnimationFrame(currentTime)) {
                            readyAnims.add(anim);
                        }
                    }
                    int numReadyAnims = readyAnims.size();
                    if (numReadyAnims > 0) {
                        for (int i = 0; i < numReadyAnims; ++i) {
                            ValueAnimator anim = readyAnims.get(i);
                            anim.startAnimation();
                            anim.mRunning = true;
                            delayedAnims.remove(anim);
                        }
                        readyAnims.clear();
                    }

                    // Now process all active animations. The return value from
                    // animationFrame()
                    // tells the handler whether it should now be ended
                    int numAnims = animations.size();
                    int i = 0;
                    while (i < numAnims) {
                        ValueAnimator anim = animations.get(i);
                        if (anim.animationFrame(currentTime)) {
                            endingAnims.add(anim);
                        }
                        if (animations.size() == numAnims) {
                            ++i;
                        } else {
                            // An animation might be canceled or ended by client
                            // code
                            // during the animation frame. Check to see if this
                            // happened by
                            // seeing whether the current index is the same as
                            // it was before
                            // calling animationFrame(). Another approach would
                            // be to copy
                            // animations to a temporary list and process that
                            // list instead,
                            // but that entails garbage and processing overhead
                            // that would
                            // be nice to avoid.
                            --numAnims;
                            endingAnims.remove(anim);
                        }
                    }
                    if (endingAnims.size() > 0) {
                        for (i = 0; i < endingAnims.size(); ++i) {
                            endingAnims.get(i).endAnimation();
                        }
                        endingAnims.clear();
                    }

                    // If there are still active or delayed animations, call the
                    // handler again
                    // after the frameDelay
                    if (callAgain && (!animations.isEmpty() || !delayedAnims.isEmpty())) {
                        sendEmptyMessageDelayed(ANIMATION_FRAME, Math.max(0, sFrameDelay
                                - (AnimationUtils.currentAnimationTimeMillis() - currentTime)));
                    }
                    break;
            }
        }
    }

    /**
     * The amount of time, in milliseconds, to delay starting the animation
     * after {@link #start()} is called.
     * 
     * @return the number of milliseconds to delay running the animation
     */
    public long getStartDelay() {
        return mStartDelay;
    }

    /**
     * The amount of time, in milliseconds, to delay starting the animation
     * after {@link #start()} is called.
     * 
     * @param startDelay The amount of the delay, in milliseconds
     */
    public void setStartDelay(long startDelay) {
        this.mStartDelay = startDelay;
    }

    /**
     * The amount of time, in milliseconds, between each frame of the animation.
     * This is a requested time that the animation will attempt to honor, but
     * the actual delay between frames may be different, depending on system
     * load and capabilities. This is a static function because the same delay
     * will be applied to all animations, since they are all run off of a single
     * timing loop.
     * 
     * @return the requested time between frames, in milliseconds
     */
    public static long getFrameDelay() {
        return sFrameDelay;
    }

    /**
     * The amount of time, in milliseconds, between each frame of the animation.
     * This is a requested time that the animation will attempt to honor, but
     * the actual delay between frames may be different, depending on system
     * load and capabilities. This is a static function because the same delay
     * will be applied to all animations, since they are all run off of a single
     * timing loop.
     * 
     * @param frameDelay the requested time between frames, in milliseconds
     */
    public static void setFrameDelay(long frameDelay) {
        sFrameDelay = frameDelay;
    }

    /**
     * The most recent value calculated by this <code>ValueAnimator</code> when
     * there is just one property being animated. This value is only sensible
     * while the animation is running. The main purpose for this read-only
     * property is to retrieve the value from the <code>ValueAnimator</code>
     * during a call to
     * {@link AnimatorUpdateListener#onAnimationUpdate(ValueAnimator)}, which is
     * called during each animation frame, immediately after the value is
     * calculated.
     * 
     * @return animatedValue The value most recently calculated by this
     *         <code>ValueAnimator</code> for the single property being
     *         animated. If there are several properties being animated
     *         (specified by several PropertyValuesHolder objects in the
     *         constructor), this function returns the animated value for the
     *         first of those objects.
     */
    public Object getAnimatedValue() {
        if (mValues != null && mValues.length > 0) {
            return mValues[0].getAnimatedValue();
        }
        // Shouldn't get here; should always have values unless ValueAnimator
        // was set up wrong
        return null;
    }

    /**
     * The most recent value calculated by this <code>ValueAnimator</code> for
     * <code>propertyName</code>. The main purpose for this read-only property
     * is to retrieve the value from the <code>ValueAnimator</code> during a
     * call to {@link AnimatorUpdateListener#onAnimationUpdate(ValueAnimator)},
     * which is called during each animation frame, immediately after the value
     * is calculated.
     * 
     * @return animatedValue The value most recently calculated for the named
     *         property by this <code>ValueAnimator</code>.
     */
    public Object getAnimatedValue(String propertyName) {
        PropertyValuesHolder valuesHolder = mValuesMap.get(propertyName);
        if (valuesHolder != null) {
            return valuesHolder.getAnimatedValue();
        } else {
            // At least avoid crashing if called with bogus propertyName
            return null;
        }
    }

    /**
     * Sets how many times the animation should be repeated. If the repeat count
     * is 0, the animation is never repeated. If the repeat count is greater
     * than 0 or {@link #INFINITE}, the repeat mode will be taken into account.
     * The repeat count is 0 by default.
     * 
     * @param value the number of times the animation should be repeated
     */
    public void setRepeatCount(int value) {
        mRepeatCount = value;
    }

    /**
     * Defines how many times the animation should repeat. The default value is
     * 0.
     * 
     * @return the number of times the animation should repeat, or
     *         {@link #INFINITE}
     */
    public int getRepeatCount() {
        return mRepeatCount;
    }

    /**
     * Defines what this animation should do when it reaches the end. This
     * setting is applied only when the repeat count is either greater than 0 or
     * {@link #INFINITE}. Defaults to {@link #RESTART}.
     * 
     * @param value {@link #RESTART} or {@link #REVERSE}
     */
    public void setRepeatMode(int value) {
        mRepeatMode = value;
    }

    /**
     * Defines what this animation should do when it reaches the end.
     * 
     * @return either one of {@link #REVERSE} or {@link #RESTART}
     */
    public int getRepeatMode() {
        return mRepeatMode;
    }

    /**
     * Adds a listener to the set of listeners that are sent update events
     * through the life of an animation. This method is called on all listeners
     * for every frame of the animation, after the values for the animation have
     * been calculated.
     * 
     * @param listener the listener to be added to the current set of listeners
     *            for this animation.
     */
    public void addUpdateListener(AnimatorUpdateListener listener) {
        if (mUpdateListeners == null) {
            mUpdateListeners = new ArrayList<AnimatorUpdateListener>();
        }
        mUpdateListeners.add(listener);
    }

    /**
     * Removes all listeners from the set listening to frame updates for this
     * animation.
     */
    public void removeAllUpdateListeners() {
        if (mUpdateListeners == null) {
            return;
        }
        mUpdateListeners.clear();
        mUpdateListeners = null;
    }

    /**
     * Removes a listener from the set listening to frame updates for this
     * animation.
     * 
     * @param listener the listener to be removed from the current set of update
     *            listeners for this animation.
     */
    public void removeUpdateListener(AnimatorUpdateListener listener) {
        if (mUpdateListeners == null) {
            return;
        }
        mUpdateListeners.remove(listener);
        if (mUpdateListeners.size() == 0) {
            mUpdateListeners = null;
        }
    }

    /**
     * The time interpolator used in calculating the elapsed fraction of this
     * animation. The interpolator determines whether the animation runs with
     * linear or non-linear motion, such as acceleration and deceleration. The
     * default value is
     * {@link android.view.animation.AccelerateDecelerateInterpolator}
     * 
     * @param value the interpolator to be used by this animation. A value of
     *            <code>null</code> will result in linear interpolation.
     */
    @Override
    public void setInterpolator(/* Time */Interpolator value) {
        if (value != null) {
            mInterpolator = value;
        } else {
            mInterpolator = new LinearInterpolator();
        }
    }

    /**
     * Returns the timing interpolator that this ValueAnimator uses.
     * 
     * @return The timing interpolator for this ValueAnimator.
     */
    public/* Time */Interpolator getInterpolator() {
        return mInterpolator;
    }

    /**
     * The type evaluator to be used when calculating the animated values of
     * this animation. The system will automatically assign a float or int
     * evaluator based on the type of <code>startValue</code> and
     * <code>endValue</code> in the constructor. But if these values are not one
     * of these primitive types, or if different evaluation is desired (such as
     * is necessary with int values that represent colors), a custom evaluator
     * needs to be assigned. For example, when running an animation on color
     * values, the {@link ArgbEvaluator} should be used to get correct RGB color
     * interpolation.
     * <p>
     * If this ValueAnimator has only one set of values being animated between,
     * this evaluator will be used for that set. If there are several sets of
     * values being animated, which is the case if PropertyValuesHOlder objects
     * were set on the ValueAnimator, then the evaluator is assigned just to the
     * first PropertyValuesHolder object.
     * </p>
     * 
     * @param value the evaluator to be used this animation
     */
    public void setEvaluator(TypeEvaluator value) {
        if (value != null && mValues != null && mValues.length > 0) {
            mValues[0].setEvaluator(value);
        }
    }

    /**
     * Start the animation playing. This version of start() takes a boolean flag
     * that indicates whether the animation should play in reverse. The flag is
     * usually false, but may be set to true if called from the reverse()
     * method.
     * <p>
     * The animation started by calling this method will be run on the thread
     * that called this method. This thread should have a Looper on it (a
     * runtime exception will be thrown if this is not the case). Also, if the
     * animation will animate properties of objects in the view hierarchy, then
     * the calling thread should be the UI thread for that view hierarchy.
     * </p>
     * 
     * @param playBackwards Whether the ValueAnimator should start playing in
     *            reverse.
     */
    private void start(boolean playBackwards) {
        if (Looper.myLooper() == null) {
            throw new AndroidRuntimeException("Animators may only be run on Looper threads");
        }
        mPlayingBackwards = playBackwards;
        mCurrentIteration = 0;
        mPlayingState = STOPPED;
        mStarted = true;
        mStartedDelay = false;
        sPendingAnimations.get().add(this);
        if (mStartDelay == 0) {
            // This sets the initial value of the animation, prior to actually
            // starting it running
            setCurrentPlayTime(getCurrentPlayTime());
            mPlayingState = STOPPED;
            mRunning = true;

            if (mListeners != null) {
                ArrayList<AnimatorListener> tmpListeners = (ArrayList<AnimatorListener>)mListeners
                        .clone();
                int numListeners = tmpListeners.size();
                for (int i = 0; i < numListeners; ++i) {
                    tmpListeners.get(i).onAnimationStart(this);
                }
            }
        }
        AnimationHandler animationHandler = sAnimationHandler.get();
        if (animationHandler == null) {
            animationHandler = new AnimationHandler();
            sAnimationHandler.set(animationHandler);
        }
        animationHandler.sendEmptyMessage(ANIMATION_START);
    }

    @Override
    public void start() {
        start(false);
    }

    @Override
    public void cancel() {
        // Only cancel if the animation is actually running or has been started
        // and is about
        // to run
        if (mPlayingState != STOPPED || sPendingAnimations.get().contains(this)
                || sDelayedAnims.get().contains(this)) {
            // Only notify listeners if the animator has actually started
            if (mRunning && mListeners != null) {
                ArrayList<AnimatorListener> tmpListeners = (ArrayList<AnimatorListener>)mListeners
                        .clone();
                for (AnimatorListener listener : tmpListeners) {
                    listener.onAnimationCancel(this);
                }
            }
            endAnimation();
        }
    }

    @Override
    public void end() {
        if (!sAnimations.get().contains(this) && !sPendingAnimations.get().contains(this)) {
            // Special case if the animation has not yet started; get it ready
            // for ending
            mStartedDelay = false;
            startAnimation();
        } else if (!mInitialized) {
            initAnimation();
        }
        // The final value set on the target varies, depending on whether the
        // animation
        // was supposed to repeat an odd number of times
        if (mRepeatCount > 0 && (mRepeatCount & 0x01) == 1) {
            animateValue(0f);
        } else {
            animateValue(1f);
        }
        endAnimation();
    }

    @Override
    public boolean isRunning() {
        return (mPlayingState == RUNNING || mRunning);
    }

    @Override
    public boolean isStarted() {
        return mStarted;
    }

    /**
     * Plays the ValueAnimator in reverse. If the animation is already running,
     * it will stop itself and play backwards from the point reached when
     * reverse was called. If the animation is not currently running, then it
     * will start from the end and play backwards. This behavior is only set for
     * the current animation; future playing of the animation will use the
     * default behavior of playing forward.
     */
    public void reverse() {
        mPlayingBackwards = !mPlayingBackwards;
        if (mPlayingState == RUNNING) {
            long currentTime = AnimationUtils.currentAnimationTimeMillis();
            long currentPlayTime = currentTime - mStartTime;
            long timeLeft = mDuration - currentPlayTime;
            mStartTime = currentTime - timeLeft;
        } else {
            start(true);
        }
    }

    /**
     * Called internally to end an animation by removing it from the animations
     * list. Must be called on the UI thread.
     */
    private void endAnimation() {
        sAnimations.get().remove(this);
        sPendingAnimations.get().remove(this);
        sDelayedAnims.get().remove(this);
        mPlayingState = STOPPED;
        if (mRunning && mListeners != null) {
            ArrayList<AnimatorListener> tmpListeners = (ArrayList<AnimatorListener>)mListeners
                    .clone();
            int numListeners = tmpListeners.size();
            for (int i = 0; i < numListeners; ++i) {
                tmpListeners.get(i).onAnimationEnd(this);
            }
        }
        mRunning = false;
        mStarted = false;
    }

    /**
     * Called internally to start an animation by adding it to the active
     * animations list. Must be called on the UI thread.
     */
    private void startAnimation() {
        initAnimation();
        sAnimations.get().add(this);
        if (mStartDelay > 0 && mListeners != null) {
            // Listeners were already notified in start() if startDelay is 0;
            // this is
            // just for delayed animations
            ArrayList<AnimatorListener> tmpListeners = (ArrayList<AnimatorListener>)mListeners
                    .clone();
            int numListeners = tmpListeners.size();
            for (int i = 0; i < numListeners; ++i) {
                tmpListeners.get(i).onAnimationStart(this);
            }
        }
    }

    /**
     * Internal function called to process an animation frame on an animation
     * that is currently sleeping through its <code>startDelay</code> phase. The
     * return value indicates whether it should be woken up and put on the
     * active animations queue.
     * 
     * @param currentTime The current animation time, used to calculate whether
     *            the animation has exceeded its <code>startDelay</code> and
     *            should be started.
     * @return True if the animation's <code>startDelay</code> has been exceeded
     *         and the animation should be added to the set of active
     *         animations.
     */
    private boolean delayedAnimationFrame(long currentTime) {
        if (!mStartedDelay) {
            mStartedDelay = true;
            mDelayStartTime = currentTime;
        } else {
            long deltaTime = currentTime - mDelayStartTime;
            if (deltaTime > mStartDelay) {
                // startDelay ended - start the anim and record the
                // mStartTime appropriately
                mStartTime = currentTime - (deltaTime - mStartDelay);
                mPlayingState = RUNNING;
                return true;
            }
        }
        return false;
    }

    /**
     * This internal function processes a single animation frame for a given
     * animation. The currentTime parameter is the timing pulse sent by the
     * handler, used to calculate the elapsed duration, and therefore the
     * elapsed fraction, of the animation. The return value indicates whether
     * the animation should be ended (which happens when the elapsed time of the
     * animation exceeds the animation's duration, including the repeatCount).
     * 
     * @param currentTime The current time, as tracked by the static timing
     *            handler
     * @return true if the animation's duration, including any repetitions due
     *         to <code>repeatCount</code> has been exceeded and the animation
     *         should be ended.
     */
    boolean animationFrame(long currentTime) {
        boolean done = false;

        if (mPlayingState == STOPPED) {
            mPlayingState = RUNNING;
            if (mSeekTime < 0) {
                mStartTime = currentTime;
            } else {
                mStartTime = currentTime - mSeekTime;
                // Now that we're playing, reset the seek time
                mSeekTime = -1;
            }
        }
        switch (mPlayingState) {
            case RUNNING:
            case SEEKED:
                float fraction = mDuration > 0 ? (float)(currentTime - mStartTime) / mDuration : 1f;
                if (fraction >= 1f) {
                    if (mCurrentIteration < mRepeatCount || mRepeatCount == INFINITE) {
                        // Time to repeat
                        if (mListeners != null) {
                            int numListeners = mListeners.size();
                            for (int i = 0; i < numListeners; ++i) {
                                mListeners.get(i).onAnimationRepeat(this);
                            }
                        }
                        if (mRepeatMode == REVERSE) {
                            mPlayingBackwards = mPlayingBackwards ? false : true;
                        }
                        mCurrentIteration += (int)fraction;
                        fraction = fraction % 1f;
                        mStartTime += mDuration;
                    } else {
                        done = true;
                        fraction = Math.min(fraction, 1.0f);
                    }
                }
                if (mPlayingBackwards) {
                    fraction = 1f - fraction;
                }
                animateValue(fraction);
                break;
        }

        return done;
    }

    /**
     * Returns the current animation fraction, which is the elapsed/interpolated
     * fraction used in the most recent frame update on the animation.
     * 
     * @return Elapsed/interpolated fraction of the animation.
     */
    public float getAnimatedFraction() {
        return mCurrentFraction;
    }

    /**
     * This method is called with the elapsed fraction of the animation during
     * every animation frame. This function turns the elapsed fraction into an
     * interpolated fraction and then into an animated value (from the
     * evaluator. The function is called mostly during animation updates, but it
     * is also called when the <code>end()</code> function is called, to set the
     * final value on the property.
     * <p>
     * Overrides of this method must call the superclass to perform the
     * calculation of the animated value.
     * </p>
     * 
     * @param fraction The elapsed fraction of the animation.
     */
    void animateValue(float fraction) {
        fraction = mInterpolator.getInterpolation(fraction);
        mCurrentFraction = fraction;
        int numValues = mValues.length;
        for (int i = 0; i < numValues; ++i) {
            mValues[i].calculateValue(fraction);
        }
        if (mUpdateListeners != null) {
            int numListeners = mUpdateListeners.size();
            for (int i = 0; i < numListeners; ++i) {
                mUpdateListeners.get(i).onAnimationUpdate(this);
            }
        }
    }

    @Override
    public ValueAnimator clone() {
        final ValueAnimator anim = (ValueAnimator)super.clone();
        if (mUpdateListeners != null) {
            ArrayList<AnimatorUpdateListener> oldListeners = mUpdateListeners;
            anim.mUpdateListeners = new ArrayList<AnimatorUpdateListener>();
            int numListeners = oldListeners.size();
            for (int i = 0; i < numListeners; ++i) {
                anim.mUpdateListeners.add(oldListeners.get(i));
            }
        }
        anim.mSeekTime = -1;
        anim.mPlayingBackwards = false;
        anim.mCurrentIteration = 0;
        anim.mInitialized = false;
        anim.mPlayingState = STOPPED;
        anim.mStartedDelay = false;
        PropertyValuesHolder[] oldValues = mValues;
        if (oldValues != null) {
            int numValues = oldValues.length;
            anim.mValues = new PropertyValuesHolder[numValues];
            anim.mValuesMap = new HashMap<String, PropertyValuesHolder>(numValues);
            for (int i = 0; i < numValues; ++i) {
                PropertyValuesHolder newValuesHolder = oldValues[i].clone();
                anim.mValues[i] = newValuesHolder;
                anim.mValuesMap.put(newValuesHolder.getPropertyName(), newValuesHolder);
            }
        }
        return anim;
    }

    /**
     * Implementors of this interface can add themselves as update listeners to
     * an <code>ValueAnimator</code> instance to receive callbacks on every
     * animation frame, after the current frame's values have been calculated
     * for that <code>ValueAnimator</code>.
     */
    public static interface AnimatorUpdateListener {
        /**
         * <p>
         * Notifies the occurrence of another frame of the animation.
         * </p>
         * 
         * @param animation The animation which was repeated.
         */
        void onAnimationUpdate(ValueAnimator animation);

    }

    /**
     * Return the number of animations currently running. Used by StrictMode
     * internally to annotate violations. Only called on the main thread.
     * 
     * @hide
     */
    public static int getCurrentAnimationsCount() {
        return sAnimations.get().size();
    }

    /**
     * Clear all animations on this thread, without canceling or ending them.
     * This should be used with caution.
     * 
     * @hide
     */
    public static void clearAllAnimations() {
        sAnimations.get().clear();
        sPendingAnimations.get().clear();
        sDelayedAnims.get().clear();
    }

    @Override
    public String toString() {
        String returnVal = "ValueAnimator@" + Integer.toHexString(hashCode());
        if (mValues != null) {
            for (int i = 0; i < mValues.length; ++i) {
                returnVal += "\n    " + mValues[i].toString();
            }
        }
        return returnVal;
    }
}
